Transcript File
Weather Chapter 12 Let’s take a look at the weather picture and why we have weather! LESSON 1: Describing Weather http://www.nbcnews.com/news/w eather/severe-weather-hitsdallas-hundreds-thousands-texaslose-power-n216851 http://www.bbc.com/news/world-uscanada-29234028 What impact did you hear in the video? Discuss with your teammates: 1. Was there anything that surprised you? 2. Was there a detail that stood out? 3. What were some of the concerns you heard? 4. How many people may be affected? 5. What might be the costs? What is Weather? • State of the atmosphere at a specific time and place • Includes such conditions as air pressure, wind, temperature, and moisture in the air • Temperature is a measure of air molecule movement • Sun’s energy causes air molecules to move rapidly; temperatures are high and it feels warm • When less of the Sun’s energy reaches air molecules, they move less rapidly and it feels cold What is Weather? • Energy is transferred between fast-moving molecules and slower-moving molecules Remember from Chapter 11/Lesson 2… • CONDUCTION – transfer of energy when molecules collide • CONVECTION – occurs when warm air rises and cool air sinks; it’s the transfer of heat, usually in liquids or gases http://video.nationalgeographic.co m/video/climate-weather-sci Water Cycle – water makes up 70% of Earth’s surface!! Water Cycle Video Link • Water moves back and forth between Earth’s atmosphere and surface • Energy from the sun causes water to evaporate from the hydrosphere and rise as vapor • Sun provides water cycle’s energy • Water on the surface absorbs heat and evaporates, entering the atmosphere • Condensation – water vapor changes back into liquid • Clouds of water become heavy and water falls to Earth as precipitation • The cycle repeats itself continuously • Rain & Drizzle- most common type of precipitation. • Freezing Rain- drizzle from stratus clouds. • Freezing Rain- raindrops freeze when they hit the ground. • Sleet- raindrops that freeze before they hit the ground. Waters 3 States Video 6:52 •snow- as ice grows and merges into clouds they form snowflakes. •hail- is the largest type of precipitation. • Lumps or balls of ice that fall from cumulonimbus clouds in warm weather. The Sun, Water Cycle, & Climate Video 2:37 The Water Cycle and Climate Change Video 15:01 If we were to pick one term to help explain why we have weather, what do you think would be a good word? You might pick heat or sun….but another good choice would be Convection After the atmosphere is warmed by radiation and conduction, the heat is transferred throughout the atmosphere by convection. • Since warmed air has more space between the molecules, it’s less dense and rises • Cooled air is more dense and tends to sink • In general, air near the equator tends to rise and air near the poles tends to sink Take a look at this! Notice the band of clouds around the equator ? This is the ITCZ or inter tropical convergence zone Why do you think there is this band of clouds near the equator? Did you figure it out? • Warm, moist air in the tropics rises • Cold air can hold less moisture than warm air • As the moist air rises, it condenses and forms clouds! Now What? • Ok, so we know that the weather moves around on these highways and that warm air rises and cold air sinks. • But why is it sunny one day, and rainy the next? Let’s break for a short review 1.Transfer of heat in liquids or gases_____ 2. _____ air is dense and tends to sink. 3. Band of clouds found around the equator______ 4. Cold air holds _____ moisture than warm air 5. The Coriolis effect causes the air and water to be deflected to the _____ of the equator How did you do? 1. CONVECTION 2. COLD 3. ITCZ 4. LESS 5. RIGHT LESSON 2: Weather Patterns Pressure demonstration • Individual – list all the things you know… what did you observe? • Remember not to make assumptions • ATT – discuss what you know together • What do you think happened? Think & Write about it… On the input page of your iNB write down: • What happened to the can? • Why did this occur? • Relate this to what you know about weather on Earth. Let’s take another look at the weather map • Notice that there are H’s and L’s on the map • There are also blue lines with spikes and red lines with half circles • Let’s take a closer look! AIR PRESSURE • Air weight that varies over Earth’s surface • Warmer air is less dense and exerts less pressure • Cooler air is more dense and exerts more pressure High Pressure Areas • When cooler air sinks and is warmed, the air can hold more moisture • This usually means sunny skies • Winds tend to move clockwise around a high Low Pressure Areas • When warm air rises and is cooled, the air can not hold as much moisture • Often, these areas are associated with precipitation and stormy weather • Winds tend to move counter clockwise around the low So, if you see a big H on the weather map over the area you live, you can expect fair weather When you see a big L in your area, there will probably be stormy weather These highs and lows move or less along the jet stream and bring us our weather changes Humidity • The amount of water vapor in the air • Temperature affects how much moisture is in the air - warmer air can hold more water vapor, tending to make it more humid • Relative humidity – the amount of water vapor in the air compared to what it can hold at a specific temperature • When air cools, it can’t hold as much water vapor, so the water vapor condenses to liquid or forms ice crystals • Dew point – the temperature at which air is saturated and condensation forms Clouds • Form when air rises, cools to its dew point, and becomes saturated • Shape and height of clouds vary with temperature, pressure, and water vapor in atmosphere Clouds • Shape • Stratus-smooth, even sheets or layers at low altitudes • Cumulus-puffy, white clouds, often with flat bases • Cirrus-high, thin, white feathery clouds made of ice crystals • Height • Cirro – high clouds • Alto – middle-elevation clouds • Strato – low clouds • Nimbus clouds are dark and so full of water that Fog Cloud Cover Symbols • You will often see the circles drawn on a weather map Fronts and Air Masses • Because air and moisture move in the atmosphere, weather is constantly changing • Air pressure – measured by barometer • An air mass is a large body of air whose temperature and moisture are fairly similar at a given altitude; properties like the part of Earth’s surface over which it formed • Fronts are boundaries separating different air masses – clouds, precipitation, and storms occur at frontal boundaries • There are four different air masses that affect the United States The Air Masses • cP( continental polar) : cold, dry stable • cT( continental tropical) : hot, dry, stable air aloft, unstable at the surface • mP( maritime polar) : cool, moist, unstable • mT( maritime tropical) : warm, moist, unstable This map shows the air mass source regions and there paths Warm Fronts • A warm front is warm air displacing cool air Widespread precipitation develops! • Shallow leading edge warm air must “overrun” cold air • These are usually slow moving 2. Warm Front: The zone where warm air is replacing colder air • In U.S., warm fronts usually move from southwest to northeast • Air gets more humid after a warm front moves through Cold Fronts • Cold air advances into region of Temperature drops; narrow band of violent storms! warm air • Intensity of precipitation greater, but short lived • Clearing conditions after front passes • Usually approaches from W or NW 1. Cold Front: The zone where cold air is replacing warmer air • In U.S., cold fronts usually move from northwest to southeast • Air gets drier after a cold front moves through Stationary Fronts • Surface positions of the front do not move • Often a region of clouds and precipitation 3. Stationary Front: When either a cold or warm front stops moving • When the front starts moving again it returns to either being a cold or warm front Occluded Fronts • Cold front overtakes warm front • Involves three air masses of different temperatures • Often found close to the low pressure center Cloudy weather with precipitation! 4. Occluded Front: Formed when a cold front overtakes a warm front • This occurrence usually results in storms over an area • In U.S., the colder air usually lies to the west MENU Ready for a little quiz? • Here we go! 1. • Winds in a low pressure system move _____ around the low L 2. • What type of front can be found close to point D ? 3. • Which of these fronts would you expect to have greater precipitation, but be short lived as the front passes? 4. • Give the name of the air mass that would have the following characteristics : • cool, moist, unstable 5. That important weather word that refers to the transfer of heat 6. In general, air near the equator tend to_____ ( rise or fall ) 7. It causes air and water to be deflected to the right north of the equator 8. Which of the weather highways usually controls our weather 9. Warm air holds ( more or less ) moisture than cold air 10. • If there is a big on the weather map where you live, would you expect fair or stormy weather H How did you do? Let’s check the answers! Answers 1. Counterclockwise 2. Cold 3. Cold 4. Maritime polar (mP) 5. Convection 6. Rise 7. Coriolis 8. Westerlies 9. More 10. Fair WILT: What I Learned Today • In your iNB write a paragraph summarizing what you learned today. • Use at least two vocabulary terms • Refer to at least one fact from the ppt or text book. LESSON 3: Weather Forecasts Severe Weather • Thunderstorms occur inside warm, moist air masses and at fronts • Warm, moist air is forced rapidly upward, where it cools and condenses • Strong updrafts of warm air and sinking, rain-cooled air cause strong winds Lightning • Movement of air inside a storm cloud causes parts of the cloud to become oppositely charged • Current flows between the regions of opposite electrical charge, forming a lightning bolt • Thunder – lightning superheats the air, causing it to expand rapidly and then contract, forming sound waves Tornado • Violent, whirling wind that moves in a narrow path over land Hurricane • Large, swirling, low-pressure system that forms over tropical oceans • Heat energy from moist air is converted to wind that can reach speeds of 250 km/h Blizzard • A winter storm with strong winds, cold temperatures, and low visibility, that lasts more than three hours Severe Weather Safety • A National Weather Service WATCH means conditions are favorable for severe weather to develop • A warning means that severe weather conditions already exist • Meteorologists study and predict weather • National Weather Service makes weather maps and issues watches and warnings Reading a weather map • ISOBAR= connects areas of equal pressure BAR comes from BARometric pressure Reading a weather map... • Isotherm: using root word and prefix what do you think this word means? • Connects areas of equal temperature; Satellites · Satellite images are used for seeing cloud patterns and movements. · For example, hurricane clouds and movement can be observed using satellite images. Radar · Radar images can be used to detect cloud cover, rainfall or storm location, intensity, and movement, as well as the potential for severe weather (for example, hurricanes or tornadoes). http://www.youtube.com/watch?v=0VDIBpvGLU Students will get into teams and research major storm systems. 1. Type 2. Cause 3. What is used to track the storm 4. Damage 5. Frequency T1 – Thunderstorms & Lightning T2 – Drought T3 – Hurricanes T4 – Tornadoes T5 – Blizzard T6 – Dust storm (think dust bowl)